I compiled a new kernel(3.2) and I have it running on an ARM board.
I wanted to enable some params on the /proc directories. Therefore I have to be logged in as root.
Hence I did the following on my newly compiled system:

sudo passwd su

and set a new root password.

Then I logged in as root.
However I get the error message su-Authentication failure.

How do I solve this problem? Has this to do with the /usr/bin file permissions?

could you please explain how I can reboot into this mode? although I reset the password SUCCESSFULLY, I cannot login as root with the new password. Please help
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user489152Oct 1 '12 at 11:12

assuming you're using grub:to reboot into single user mode you reboot the machine and when the GRUB boot loader comes up you need to edit the command line to load the kernel and append a 1 after all the arguments
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h3rrmillerOct 1 '12 at 11:54

I fixed it. I had to set the sticky bit of the su binary! So when I did chmod +s /bin/su, I could "su" with the changed root password.Thanks for all your help
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user489152Oct 1 '12 at 14:45

you could've also used sudo -i to gain root via sudo without elevating with su
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h3rrmillerOct 1 '12 at 15:46